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Terry's DRSSTC About finished ;-)

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

I ran my DRSSTC into a primary coil and cap (but just battery power):


The six 9V batteries easily pumped 10 amps at about 60kHz into the primary. The unloaded primary's LC resistance is 100 ohms so 10 amps represents 1000V. It could have gone much higher but I did not have anything insulated or set up to push any real voltages. The over current works fine even way down at 10 amps.


Sort of an interesting picture. The first downward pulse on the yellow trace (output voltage) is the startup circuit pulse. Then the digital CT has enough signal to drive it onward. For the first 80uS, it is driving current into the primary. Then it is switched off By the fiber optic remote controller and the energy in the primary LC is sucked back up into the box. Note the voltage phase shift in the middle. That surprised me at first, but I guess it knows what it is doing ;-) The first 5 voltage pulses are driven from the IGBTs while the trailing 4 pulses are the reverse diodes in the IGBTs feeding the primary LC voltage back into the buss rails.

The gate drive signals are fast and solid with rise and fall times at about 100 - 150 nS (these are at the IGBT gates under power). There is some high speed glitching. Hard to tell if that is from the differential probe just picking up noise or if it is really there. I will order up a load of ferrites from DigiKey just in case. I did clean up some gate drive wiring which should help too. The gate drive cards have no problem at all driving the gates.


So I put it all together and powered it up!!


Nothing was connected and no drive signal but at this point the buss is fully loaded for bear and the IGBTs are fully charged and the logic is in full control. If anything were wrong, it would have blown up here. I put the cover on the contain any flying burning fragments, but all went fine ;-)

The only real change was to make the charging resistor 50 ohms and fuse it. The 100mA of current needed by the gate drive cards loaded down the 250 ohm resistor and it could only charge the buss to 240V. The 50 ohm resistor charges to 305 so no problem when the bypass is thrown in "snapping" the buss voltage to the full 340 VDC.

I still have not put the remote control board in it's box so I still need to do that. I will also look more into the gate glitches. I think I will set the IGBT temperature limit at 50C and the current trip at 50 amps for starters. The fan is sort of blocked right now, but if it does not need more flow I will just leave it as is. It "seems" like it will be fine. I think I can just run my big coil as is with it to start but probably just run the primary with a big resistor in series at first.

I took a bunch of pictures inside on out: